A technology for manufacturing a carbon nanotube by chemically manufacturing an Fe nanoparticle and using the Fe nanoparticle as a catalyst is known. For example, JP2009-215146A, hereinafter referred to as Reference 1, discloses a technology for manufacturing an Fe nanoparticle of Fe2O3 having a particle size, or a particle diameter, equal to or less than 10 nanometers (nm) in diameter from a metallic precursor, a surfactant, and a solvent as basic materials. A technical paper entitled “Solution-phase Synthesis of Magnetic Iron Oxide Nanoparticles from Hematite Powder” published on page 402 in the proceeding of the 22nd Fall Meeting of the Ceramic Society of Japan, hereinafter referred to as Non-patent literature 1, discloses a technology for manufacturing Fe nanoparticles of Fe3O4 having a particle diameter equal to or less than 20 nm by controlling ratio of an iron oxide and an oleic acid in a mixture of the iron oxide, the oleic acid, and 1-octadecene. A liquid-phase method is suitable for manufacturing Fe nanoparticles in large quantities, however, manufacturing a ferrous oxide (FeO) nanoparticle, or an Iron(II) oxide nanoparticle, by using a liquid-phase method is considered difficult. In addition, as disclosed in JP2009-227470A, hereinafter referred to as Reference 2, a process of forming a carbon nanotube by using an iron oxide particle is known to include a fast initial growth process and a slow growth process that comes thereafter. Furthermore, using an Fe nanoparticle having a large particle diameter as a catalyst so as to manufacture a carbon nanotube having a large outer diameter is known to decrease growth potential of the carbon nanotube, which is considered as a drawback.
A need thus exists for a method of manufacturing a ferrous oxide nanoparticle, a method of forming a carbon nanotube, and the ferrous oxide nanoparticle which is not susceptible to the drawbacks mentioned above.